With a surprise election sprung on the parties, politicians, advisers and party policy experts will be scribbling late into the night trying to knock together manifestos to put before the voters.

But we're already getting an insight into what might and might not be in them, especially from the Conservatives.

For a start, the Prime Minister has confirmed the commitment for the UK to meet its UN target of spending 0.7% of its GDP on foreign aid - a long-standing shibboleth of Cameron modernisation - will stay.

This will be a source of great consternation to some of her backbenchers.

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They say that spending £13bn on aid abroad when the UK still sports a deficit of over £50bn (and rising next year) is nonsensical, especially at a time when public services are enduring unprecedented financial strain.

A Tory MP I've spoken to described the PM essentially making her opening policy gambit for an election with that as "madness".

Especially on a day when the Chancellor, Philip Hammond, has indicated the 2015 Conservative tax lock pledge - where they committed not to increase income tax, national insurance or VAT - would not be in the Tory manifesto at this election.

Speaking at an IMF conference in Washington, he said he felt the tax lock pledge had "constrained" his ability to balance the books and ought to be looked at again.

Well…duh. Many independent commentators at the time said the pledge made the task of eliminating the deficit very difficult.

But Mr Hammond and his colleagues not only stood on the promise but also voted for a tax lock in the House of Commons which signed into law the idea the Chancellor couldn't change those bands for this parliament.

Many economists thought this barmy and it now seems that Mr Hammond agrees.

That might be connected to his embarrassing U-turn in his first budget less than two months ago.

He attempted to increase national insurance rates on the self-employed only to be forced to retreat as a result of the manifesto lock.

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So we might expect tax rises if the Conservatives win the election.

And sometimes we learn from what politicians don't say as much as what they do.

The Prime Minister refused to confirm the Tories would include a manifesto pledge on keeping their so-called "pension triple lock", where pensions increase by average wage increases, the inflation rate or 2.5%, whichever is highest.

This was core Tory-party policy for the Cameron era. It's also extremely expensive and many analysts say makes generational inequalities worse.

The fact that the Prime Minister is able to make (or not make) these pledges is telling.

It seems inconceivable that David Cameron would have retreated from these vote-winning measures in 2015 when he felt the Labour party was breathing down his neck.

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Likewise he assumed he wouldn't win the 2015 election outright and therefore that manifesto was not meant to be the governing document.

He assumed he would have to trade away measures in negotiations with the Lib Dems so felt he could be looser with the manifesto's contents.

For Theresa May and Philip Hammond, they neither perceive a threat from the opposition nor do they believe they will have to build a coalition.